Smoke detector and blower motor control system



United States Patent SMOKE DETECTOR AND BLOWER MOTOR CONTROL SYSTEMEdward J. Zeitlin, Yorktown, Herbert S. Thorn, Flushing, and Lee R.Leighton, Mohegan Lake, N. Y., assigners to Heat Timer Corporation, NewYork, N. Y.

Application May 18, 1951, Serial No. 227,046

Claims. (Cl. 318-480) In other words, it provides for an automaticindication resulting from the system being affected by a temporary smokecondition, but permits the system to reset before the burner is shutdown.

In general the system comprises means for producing a beam of light thatis directed to a photo-electric element of the photoemissive type. Thelight means being positioned on one side of a chimney flue and thephotoelectric element on the opposite side so that the flue gases mustpass through the light beam. In addition there are provided meansconnecting said photo-electric element to an electronic control. Theelectronic control includes a thyratron tube which in turn controls theenergization or de-energization of a relay. The relay in turn controlsthe closing and opening of a plurality of circuits, one of thesecircuits includes a timing motor, and a switch operating cam driven bysaid motor. The thyratron tube is used to control the operation of therelay and functions as follows: the tube has two voltages impressed onits grid, one from the photo-cell and one from an auxiliary source whichin this instance is controlled by a potentiometer connected across thefilament circuit. When there is a clear condition or no smoke, thephoto-cell is illuminated and current flows from the photo-cell andcauses a voltage to be impressed on the grid in such a manner to changethe characteristic of the tube and become conductive. With the tube in aconductive condition, the circuit connected to the tube, that is, thecircuit between the anode and the cathode will convey a current to therelay to energize same andv vice versa when the photo-cell is notilluminated due to a smoke condition, the thyratron will becomenon-conductive and the energizing circuit will be broken. The relaycontrols the switch contacts associated therewith to close predeterminedcircuits, one of which includes the timing motor. When this circuit isclosed by the relay the motor will be operated and will rotate a switchcam mounted on said motor shaft, the cam in this instance making onerevolution in a two minute interval. A pair of switches are mounted tocontact said cam, one of said switches providing a holding circuit toretain the timing motor connected to a source of potential until the camhas completed one revolution, the other switch which.

is a gang switch will be closed during the rotation of the cam and isthe means of holding the burner circuit closed untilthe cam completes apredetermined portion of its cyclewhen the switch will open.

It is an object of this invention to provide a smoke detecting systemthat will accomplish the above mentioned results and must be unusuallysensitive and reliable for automatic operation, to prevent false alarmsor unnecessary shut downs of the burner motor.

A further object of this invention is to provide a lightsensitive smokedetecting system for chimneys that will produce an alarm signal whensmoke is detected and will at the same time initiate a timed burnershut-oft mechanism.

A still further object of this invention is to provide a light sensitivesmoke detecting system which includes an electronic control that maybecome non-conductive with the presence of smoke to in turn de-energizethe relayand initiate the operation of a timer burner motor shutoff, butin addition provides means to reestablish the burner motor circuit inthe event the smoke con-' dition is dissipated before the timer hascompleted its cycle.

Another object of this invention is to provide a light sensitive smokedetecting system for chimneys to produce an alarm signal indicating thepresence of smoke, to initiate a timed motor burner shut-off and toprovide means to re-establish the operation of the burner includes achimney 10 with a flue 11. The chimney isprovided with a pair of opposedapertures or ports 12 and 14. Into port 12 there is inserted a lightsource 15 which may, as in this instance be a watt volt incandescentlamp 16 that is oriented so that its light will fall upon the oppositeaperture 14. Into the aperture or port 14 there is mounted a phototube17 which is simply a device of variable conductance in response toincident light. A circuit is connected to both the light source 15 andthe phototube 17 and includes a positivegrid control thyratron tube 20which is in turn connected to a relay 22, that is, the lead 50 connectsthe anode or plate of the tube with one side of the relay 22. The relay22 on its opposite end is connected to switch 36 and to the oppositepower lead 25. Relay 22 is provided with In its open position asillustrated,

a contact arm 41. the relay is de-energized. Contact arm 41 ismechanically connected to a pair of contact arms 42 and 45, thus thearms 41, 42 and 45 will operate in unison. There are provided a pair ofswitches 43 and 44 positioned either side of contact arm 41 and a pairof switches 47, and 48 positioned either side of contact arm 42, while asingle switch 46 is positioned adjacent to contact arm 45. Contact arm41 in its open position retains switches 43 and 48 closed while switches44, 46 and 47 will remain open until the relay is energized. Thereforewhen the relay is energized, switches 44, 46 and 47 will be closed. ;Asource of potential (115 volt A. C.) is provided and connected to theapparatus by means of feed lines 25 and 26. A line switch 27 is providedin feed line 25. A oneone-half R. P. M. or one revolution in twominutes. A

cam 30 is afiixed to shaft 29 to be driven or rotated thereby.

Cam 30 is provided with one cut-out segment 31 in its periphery 32.Mounted adjacent to the periphery 32 of the cam 30 are a pair ofswitches 33 and '34 that bear Patented Dec. 13, 1955 The motor 28 has adrive shaft 29 which will be driven at the rate of' on the periphery ofthe cam and are normally in a closed relation, but will drop to an openrelationship when the cutout segment is moved into an adjacent positionas illustrated with switch 33. Switch 34 is a gang switch comprised ofthree switches 35, 36 and 37 all operated in a mechanically connectedrelationship to be closed or opened in unison. A burner motor 40 isprovided as the object that is to be controlled by the apparatus andcircuit herein described. Burner motor 40 is connected to the source ofpotential 26, and 27 but in series with switch 46 of the relay 22 aswell as in series with the switch 35 of the gang switch 34. The burnermotor 40 is also provided with a standard recycling circuit 31 to bedescribed in detail hereafter. The recycling circuit includes a relay 8,a bimetal recycling contactor bar and a gang switch 1, 2 and 3 operatedby relay 8. The circuit between components may be followed by referenceto the drawing. Motor 40 is connected on one side by means of lead 80 tothe power line 25 and on the opposite side is connected by means of leadX to switch 2. When relay 8 is energized switches 1, 2 and 3 will beclosed and the motor circuit from switch 2 will be connected throughlead C to the other side 26 of the power line. When the line switch 27is closed and relay 22 becomes energized, switch 46 will be closed andof course switch 36 is normally closed, thus a circuit from line 25through lead 80 to line 81, through switch 46, through lead 82, throughbimetal contact 4, through lead 7, through relay 3, through lead 6 tothe opposite side 26 of the power line will be completed. Relay 8 isthus energized closing contacts 1, 2 and 3. Contact 2 starts the burnermotor as described. Contact 3 applies line voltage to the bimetalcontact winding causing it to heat and thus open this contact 4,although the bimetal switch opens without delay when heated, it takesapproximately 90 seconds for the bimetal switch to cool and remake thecontact. Contact 1 is already closed thus shunting the contact 4circuit, that is, the lead 82 is connected to contact 1 and when closedthe circuit will flow through lead 7 and through relay 8 to lead 6 andto opposite side of the line 26, thus retaining relay 8 energized. Thethyratron tube has its filament 60 connected on one side to the lamp 16while the opposite side of the filament is connected to the power line26. The opposite side of lamp 16 is connected to the opposite side ofthe power line 25. A potentiometer 61 is connected across the filamentcircuit and the potentiometer is also connected by a lead 62 to aresistance 63 which is in turn connected to the grid of the tube. Thisprovides one circuit to permit impressing one voltage on the grid of thetube while the phototube 17 is connected by a lead 64 to a common lead65 which in turn is connected to the power line and the opposite side ofthe phototube 17 is connected by a lead 66 to the grid of the thyratronto provide the means to adjust the grid of tube 20s potential withrespect to the cathode 4A grid circuit making the thyratron conductive.Switch 48 of relay 22 is connected by means of a lead 70 to a terminal71. The opposite terminal 72 is connected to a ground and a lamp 73 isshunted across the two terminals. An alarm (not shown) may be connectedto these terminals 71 and 72 to be energized when switch 48 is closed asillustrated in the drawing. A by-pass switch 75 is also provided. Theby-pass switch 75 will short out both switches and 46, since it ispositioned across the two leads to switches 35 and 46. Thus the switch75 may be closed to in turn close the burner motor circuit. There isalso provided a reset switch 54 which in an open position permits manualcontrol of the apparatus, while in a closed position permits the controlto operate automatically. In a closed position, switch 54 will completetwo circuits, one starting with switch 37 which is connected to one sideof a contact arm A of switch 54 to thus short out switch 37. The othercircuit is closed by a contact arm B of switch 54 completing a circuitthat shorts "out switch 36.

The operation of the device may be understood by reference to thedrawing. It is first necessary that the line switch 27 be closed. Thiswill in turn illuminate lamp 16 and provide a predetermined voltage onthe filament of the thyratron tube 20. Assuming the chimney 11 to beclear of any smoke condition, the light rays of lamp 16 will fall uponthe phototube 17 activating same. Thus the phototube 17 will impress apotential on the grid of the thyratron while the potentiometer 61provides the means to adjust the grid of tube 20s potential with respectto the cathode for a grid circuit current corresponding to a certainillumination of phototube 17. Thus in this condition the thyratronbecomes conductive and the power circuit from 26 will pass from thecathode of the thyratron to the anode and thus through lead 50 to relay22 through the relay through lead 77 to the normally closed switch 38passing out the opposite side of switch 36 to the leads which in turnconnects to the opposite side of the power line 25. Thus relay 22 willbe energized and when relay 22 is energized, contact arm 41 will bepulled downward thus closing switches 44, 46 and 47. The closing ofswitch 46 will close the power circuit to the burner motor 40, that is,the reset switch 31 of the burner motor is connected on one side by alead 80 to the power line 25 and on its opposite side it is connectedthrough contact switch 2 to the opposite side 26 of the power line. Thusthe circuit to the burner motor is controlled by switch 46. The closingof switch 47 provides a holding circuit for relay 22, that is, with thethyratron in its conductive relation as above described, the circuitpassing through relay 22 to energize same passes through lead 77 andthrough a lead 83 to the switch 47 which is closed when the relay 22 isenergized. The circuit passes through the contact arm 42 through a lead84 to lead 65 which as already described is connected to the oppositeside 25 of the power line.

When relay 22 is de-energized due to a smoke condition, then contact 43is closed, thus completing the circuit to the timing motor 8. Thecircuit is as follows: starting with power line 25 through lead 87 tomotor 28, through lead 88, through lead 89 to switch 43, through theclosed contact through lead to switch 37, through the closed contact tolead 76, through lead 76, through lead 90 back to the opposite powerline. In the instance in which the smoke clears before cam 30 rotates tothe position where arm 35A drops into notch 31, of course relay 22 willagain be energized, opening contacts 43, however contact 33 in parallelwith contact 43 maintains the circuit closed to the motor 28 and the camwill complete one revolution, until contact 33 is broken. If smokecontinues and switch 54 is set in an open position for manual reset,then contacts 35, 36 and 37 are open. Opening contact 35 will breakburner motor circuit. Contact 36 will lock out relay 22, thus relay 22cannot be reenergized and the burner motor will remain off until switch54 is momentarily closed (manually). Contact 37 will open the circuit tothe timing motor 28 so that contact arm 35 will rest in notch 31 untilswitch 54 is momentarily closed (manually), when motor 28 will restartand rotate cam 30 until contact 33 is opened by notch 31. If smokecontinues and switch 54 is closed (the automatic reset position), whenarm 35 drops into notch 31 then contact 35 opens shutting off burnermotor, however, contact 36 is shunted by arm B of switch 54, and contact37 is shunted by arm A of switch 54, therefore the cam 30 will continueits revolution until contact 33 stops motor 28. Of course the smokecondition in chimney is the main reason for de-energizing relay 22, butif this condition is eliminated before the (90 second) bimetal recyclingtime has elapsed, the relay 22 will again be energized and at the end ofthe 90 second cycle the circuit to relay 8 will again be completed andthe control circuit will thus automatically restart the burner motor 40.Any failure in the circuit, such as the failure of the thyratron tofunction would of course cause the relay 22 to become de-energized andcontact 48 would be closed thus sounding the alarm (not shown) that maybe connected to terminals 71 and 72 and the circuit must be repairedbefore the relay 22 will again function properly.

This alarm circuit may be followed starting with the power line 25through line 65, through closed switch 48, through line 70 to alarmterminal 71. Since the alarm is grounded on the opposite terminal 72 andthe opposite power line 26 is also grounded then a circuit will becompleted to the alarm (not shown). Also the alarm lamp L will beilluminated. The alarm may be a bell or light or buzzer as desired.

In manual reset position, the burner motor is shut off and stays off andalarm continues to ring.

In automatic reset position the alarm rings when smoke develops, howeverthe burner will not be shut 01? until arm 35 drops, this shuts offburner motor and stops smoke condition, relay 22 is re-energized andalarm stops. Burner motor remains off until recycling mechanismreestablishes circuit. After recycling time has elapsed the burner motorwill start again, if smoke has cleared there is no alarm, if smokecontinues, the alarm continues until timer breaks it again.

Although we have described the operation of this control unit withrelation to a smoke detecting means to cause the burner to shut off, wemay depart from this particular means without departing from the spiritof this invention and this invention shall be limited only by theappended claims.

What is claimed is:

1. An apparatus for detecting smoke in a chimney including a lightsource for producing a beam of light across the flue of said chimney, aphototube of variable conductance responsive to incident light from saidbeam, means for conducting a stream of burned gases from burner throughsaid flue past said light beam, an electronic element such as a positivegrid control thyratron responsive to voltage from said phototube, apotentiometer connected to the power line and connected to theelectronic element, said electronic element responsive to the potentialimpressed by said phototube and means to adjust the grid of thethyratrons potential with respect to the cathode with said potentiometerto make said electronic element conductive and said electronic elementresponsive to an unbalance of said voltages to become non-conductive, arelay connected to said electronic element and normally energized by acircuit passing through said electronic element, a plurality of contactson said relay, one of the contacts on said relay controlling theoperation of a burner motor.

2. In a device according to claim 1 a timing motor connected to a secondset of contacts on said relay to be controlled by said relay, a one-halfR. P. M. cam connected to and driven by said timing motor, said camprovided with a notched out portion, a plurality of normally closedcontacts opened by the rotation of said cam, means to start said timingmotor after said burner motor has been shut off, means to retain saidtiming motor operating for a complete revolution of said cam, and meansto reset said cam to its initial position ready for another cycle ofoperation.

3. An apparatus for detecting smoke in a chimney including a lightsource for producing a beam of light across the fiue of said chimney, aphototube of variable conductance responsive to incident light from saidbeam, means for conducting a stream of burned gases from a burnerthrough said flue past said light beam, an electronic element such as apotential grid control thyratron responsive to voltage from saidphototube, a potentiometer connected to the power line and connected tothe electronic element, said electronic element responsive to thepotential impressed by said phototube and means to adjust the grid ofthe thyratrons potential with respect to the cathode with saidpotentiometer to make said electronic element conductive and saidelectronic element responsive to an unbalance of said voltages to becomenon-conductive, a relay connected to said electronic element andnormally energized by a circuit passing through said electronic element,a plurality of contacts on said relay, one of the contacts on said relaycontrolling the operation of a burner motor, a bi-metallic heatcontrolled reset circuit connected to said burner motor, said resetcircuit when broken constructed so that it will reclose after apredetermined time interval, said reset circuit also connected to theburner control contact of said relay.

4. In a device according to claim 3 a timing motor connected to a secondset of contacts on said relay to be controlled by said relay, a one-halfR. P. M. cam connected to and driven by said timing motor, said camprovided with a notched out portion, a plurality of normally closedcontacts opened by the rotation of said cam, means to start said timingmotor after said burner motor has been shut off, means to retain saidtiming motor operating for a complete revolution of said cam, and meansto reset said cam to its initial position ready for another cycle ofoperation.

5. An apparatus for detecting smoke in a chimney including a lightsource for producing a beam of light across the flue of said chimney, aphototube of variable conductance responsive to incident light from saidbeam, means for conducting a stream of burned gases from a burnerthrough said flue past said light beam, an elec tronic element such as apositive grid control thyratron responsive to voltage from saidphototube, a potentiometer connected to the power line and connected tothe electronic element, said electronic element responsive to thepotential impressed by said phototube and means to adjust the grid ofthe thyratrons potential with respect to the cathode with saidpotentiometer to make said electronic element conductive and saidelectronic element responsive to an unbalance of said voltages to becomenon-conductive, a relay connected to said electronic element andnormally energized by a circuit passing through said electronic element,a plurality of contacts on said relay, one of the contacts on said relaycontrolling the operation of a burner motor, a timing motor connected toa second set of contacts on said relay to be controlled by said relay, aone-half R. P. M. cam connected to and driven by said timing motor, saidcam provided with a notched out portion, a plurality of normally closedcontacts opened by the rotation of said cam, a manual reset switchshunted across the contacts operated by said cam.

References Cited in the file of this patent UNITED STATES PATENTS 216;John Wiley & Sons, New York, 1949.

